Larviciding intervention targeting malaria vectors also affects Culex mosquito distribution in the city of Yaoundé, Cameroon.

Although Culex species are considered to be equally affected by control measures targeting malaria vectors, there is still not enough evidence of the impact of interventions such as larviciding on the distribution of these mosquito species. The present study assessed the impact of a larviciding trial targeting malaria vectors on Culex mosquito species in the city of Yaoundé, Cameroon. A cluster randomized trial comparing 13 treated clusters and 13 untreated clusters was implemented. Data were collected at baseline and during the larviciding intervention, from March 2017 to November 2020. The microbial larvicide VectoMax G was applied once every 2 weeks in the intervention areas. Adult mosquitoes were collected using CDC light traps in both intervention and non-intervention areas and compared between arms. Globally, larviciding intervention was associated with 69% reduction in aquatic habitats with Culex larvae and 36.65% reduction of adult Culex densities in houses. Adult Culex densities were reduced both indoors (35.26%) and outdoors (42.37%). No change in the composition of Culex species was recorded. The study suggests a high impact of larviciding on Culex mosquito species distribution. The impact of the intervention can be improved if typical Culex breeding habitats including pit latrines are targeted.

Influence of house characteristics on mosquito distribution and malaria transmission in the city of Yaoundé, Cameroon.

BACKGROUND: Improving house structure is known to limit contact between humans and mosquitoes and reduce malaria transmission risk. In the present study, the influence of house characteristics on mosquito distribution and malaria transmission risk was assessed in the city of Yaoundé. METHODS: The study was conducted from March 2017 to June 2018 in 32 districts of the city of Yaoundé. Mosquito collections were performed indoor in 10 to 15 houses per district using CDC light traps. A total of 467 houses, selected randomly were used. A pretested questionnaire was submitted to participants of the study to collect information on the household: the number of people per house, education level, type of walls, presence of ceilings and eaves, number of windows, usage of long-lasting insecticidal nets (LLINs), number of bedroom and number of window. Mosquitoes collected were identified morphologically. Anophelines were tested by ELISA to detect infection by Plasmodium parasites. General Estimating Equations adjusting for repeated measures in the same house fitting negative binomial analysis were used to assess the influence of house characteristics on mosquito distribution. RESULTS: A total of 168,039 mosquitoes were collected; Culex spp emerged as the predominant species (96.48%), followed by Anopheles gambiae sensu lato (s.l.) (2.49%). Out of the 1033 An. gambiae s.l. identified by PCR, 90.03% were Anopheles coluzzii and the remaining were An. gambiae sensu stricto (s.s.) (9.97%). The high number of people per household, the presence of screens on window and the possession of LLINs were all associated with fewer mosquitoes collected indoors, whilst opened eaves, the high number of windows, the presence of holes in walls and living close to breeding sites were associated with high densities of mosquitoes indoor. Out of 3557 Anophelines tested using ELISA CSP, 80 were found infected by Plasmodium falciparum parasites. The proportion of mosquitoes infected did not vary significantly according to house characteristics. CONCLUSION: The study indicated that several house characteristics such as, the presence of holes on walls, opened eaves, unscreened window and living close to breeding sites, favored mosquito presence in houses. Promoting frequent use of LLINs and house improvement measures, such as the use of screen on windows, closing eaves, cleaning the nearby environment, should be integrated in strategies to improve malaria control in the city of Yaoundé.

Correction to: Malaria prevention in the city of Yaoundé: knowledge and practices of urban dwellers.

Following publication of the original article [1], the authors flagged an error concerning Table 3.

Malaria prevention in the city of Yaoundé: knowledge and practices of urban dwellers.

BACKGROUND: Malaria prevention in Cameroon mainly relies on the use of ITNs. Although several free distribution campaigns of treated nets have been conducted across the country, bed net usage remains very low. A household survey was conducted to assess knowledge of the population and practices affecting treated net usage in the city of Yaoundé. METHODS: A community-based descriptive cross-sectional survey was conducted in January 2017 in 32 districts of the city of Yaoundé. Parents (household head, spouse or an elder representative) who consented to the study, were interviewed using a structured pre-tested questionnaire. Interviews were conducted in French or English. A questionnaire consisting of 22 questions was administered to know (i) people's knowledge and attitude on preventive measures; and, (ii) attitudes concerning the treatment of malaria and estimated amount spent for malaria prevention and treatment. RESULTS: A total of 1643 household heads were interviewed. Over 94% of people interviewed associated malaria transmission to mosquito bites. The main methods used against mosquito bites were: treated bed nets (94%; n = 1526) and insecticide spray or coils (32.2%; n = 523). The majority of people interviewed reported using bed nets mainly to prevent from mosquito bites (84.4%, n = 1257), rather than for malaria prevention (47.3%). Knowledge and attitude analysis revealed that people with university or secondary level of education have better knowledge of malaria, prevention and treatment measures compared to those with the primary level (OR = 7.03; P < 0.001). Also, wealthy households were more aware of good practices concerning malaria prevention and treatment compared to poor ones. In the majority of districts of Yaoundé, over 50% of people interviewed per district, had good knowledge of malaria and prevention measures but less than 50% applied good practices concerning malaria treatment and prevention. The amount spent annually by a household for vector control was CFAF 11,589 ± 1133 (US$21.87 ± 2.14) and CFAF 66,403 ± 4012 (US$125.29 ± 7.57) for malaria treatment. CONCLUSION: The study indicated that, despite good knowledge of malaria and prevention measures, few people apply good practices. More sensitization needs to be done to improve adherence to good practices concerning malaria prevention and treatment.